The International Symposium on Trophic Relationships in Inland Waters, held from 1st-4th September 1987, at the Balaton Limnological Research Institute of the Hungarian Academy of Sciences, Tihany (Hungary), was intended to give an insight into current research on limnology of inland waters. The meeting was organized on the occasion of the 60th anniversary of the Institute in order to promote the exchange of ideas and discussion of new results. Papers presented during the Symposium dealt with four main topics: (1) Interactions of inorganic nutrients, primary producers and bacteria, (2) Interactions between primary and secondary producers, (3) Trophic relationships between plankton and fish, (4) Studies on complex trophic systems. Participants from 18 countries presented 40 oral lectures and 15 posters, that reviewed the structure and functioning of inland water ecosystems from different aspects. Since in such functioning nutrients are main forcing factors, the pathways of nutrients., as well as trophic connections, are widely studied nowadays. The IX papers of these proceedings thus present a series of different approaches to the main results of current limnological research in this very important field. The structure of these proceedings was somewhat altered when papers were ranked into three main groups: (1) Long-term changes, (2) Annual and seasonal cycles and (3) Short-term changes and pilot scale operations. The sequence of papers within these groups follows the four main subjects discussed during the Symposium.